In the construction of electrochemical cells for the direct generation of electrical energy, it is common to retain the electrolyte in a separator positioned between the working electrodes of the cell. In these cells a primary requirement of the separator has been to permit unrestricted--to the extent possible--electrolyte conduction or ion-transfer through the separator to provide free ion-transfer between the working electrodes. For example, U.S. Pat. Nos. 3,216,862 and 3,216,863 disclose a battery plate separator which is non-porous. However, the separator is readily ion-permeable. The primary object in using the non-porous separator, according to the patents, is to prevent metallic conduction between the plates of opposite polarity while freely permitting electrolytic conduction. The separator of these patents is essentially a three-part structure comprising two perforated sheets of an inert substance with a non-perforated ion-permeable membrane interposed between the sheets.
U.S. Pat. No. 3,223,556 discloses a fuel cell with separate anode and cathode compartments, with each contacting the surface of a porous material which is coated respectively by the anode and cathode catalyst layers. According to a teaching of the patent, the porous sheets of the anode and cathode have situated between them a gas-impermeable membrane which provides a gas-tight separation between the anode and cathode compartments. The gas-impervious sheet may contain a cationic exchange membrane. It is clear from the teaching of the patent that the gas-impervious sheet must be permeable to ion-transfer.
Numerous other patents are available in the prior art which teach the use of various types of separators between the electrodes in an electrochemical cell. None, however, has as a function the restriction of electrolyte passage or the restriction of ion-transfer through the membrane. To the contrary, the object is to permit free movement to the extent possible of ion species between the working electrodes of the cell. In the case of cells with soluble cathode depolarizers, such as Li/SO.sub.2, Li/SOCl.sub.2 and Li/SO.sub.2 Cl.sub.2, it is necessary to transport not only ions but also the cathode depolarizer within the cell.